Royal Society. 209 
Withstandiig the immense number of dissertations on this phee- 
nomenon which had been published, still much is wanting to- 
wards a full and satisfactory solution of the question, In no- 
ticing the various methods proposed for explaining capillary at- 
traction, he remarked that Clairaut was the only philosopher 
who supposed that the attraction of tubes extended to any visi- 
ble distance ; on the contrary, Newton and all other mathema- 
ticians considered the sphere of attraction to be confined to the 
particles immediately in contact with the tube, and that it did 
not extend to any sensible distance. ‘This has been the generally 
received doctrine, and the author thinks it confirmed by the re- 
flection of light, as observed in glass. But the true theory of 
this phenomenon was not known till Professor Leslie, in the 
Philosophical Magazine for 1802, first stated, in a pepular man- 
her, that the attraction is in proportion to the deusity of the 
fluid, and that temperature considerably modifies capillary at- 
traction, This discovery Mr. Ivory considers as furnishing the 
means of giving a complete theoretical and experimental ex- 
planation of this long debated phenomenon. Having observed 
that most philosophers had dwelt on the theory, and that very 
few direct experiments were ever made to ascertain the mode or 
nature and extent of capillary attraction, he commenced a series 
of actual experiments.on the subject. He measured the cuives 
formed by glass when immersed. in a fluid, calculated the mole- 
cular attraction of the fluid, &c. and in this manner performed 
a great variety of experiments; but many more, he observed, 
may still be made without exhausting the subject. His theo- 
retical method differed from that of Laplace, in being susceptible 
of application to physical experiment; whereas that of the French 
mathematician was founded on the calculus. The remainder of 
this ingenious paper was of a nature not fit for public reading. 
March 7. A> letter from Dr. Brewster to the President was 
read, On the Nature of double refracting Crystals, and the Me- 
thod of communicating this Power to Glass, &c. The new and 
curious researches of this philosopher having led him to investi- 
gate particularly the nature of doubly refracting erystals, he has 
at length discovered that if two plates of glass 0:30 of an inch 
thick be bent together, they yield the series of seven colours 
mentioned by Newton. He found in every case that pressure 
and thickness imparted to glass the power: of polarizing light ; 
pressure also on plates of glass gives them the power of double 
refraction. By mechanical pressure he could thus communicate 
to plates of glass, crystals of muriate of soda, &c. the property 
of doubly refracting crystals. 
March 14. In the conclusion of Dr. Brewster’s experiments, 
which were illustrated by figures of the various appearances, &e. 
_ Vol. 47. No. 215. March 1816. O this 
